1. Field of the Invention
The present invention relates to an optical transmission module.
2. Description of the Related Art
As a modulation for an optical signal used in optical communication, pulse amplitude modulation (PAM) may be employed. PAM is a modulation in which signal coding is performed based on difference of optical intensity.
In JP 2003-037337 A, there is disclosed a semiconductor laser in which the width of each stripe varies in a tapered form and side surfaces sandwiching the stripes are inclined with respect to a main surface of a substrate.
Further, in JPH09-289354A, there is disclosed a semiconductor laser element in which the stripe width continuously increases from a rear end surface toward a front end surface.
Further, in Ryoichi Ito and Michiharu Nakamura (co-edited), Semiconductor Laser [Basics and Applications], Baifukan, 1989, a relaxation oscillation frequency and a modulation degree of a semiconductor laser are described.